Systems Using Imaging Data to Facilitate Surgical Procedures

ABSTRACT

Systems and processes for tracking anatomy, instrumentation, trial implants, implants, and references, and rendering images and data related to them in connection with surgical operations, for example total knee arthroplasties (“TKA”). These systems and processes are accomplished by using a computer to intraoperatively obtain images of body parts and to register, navigate, and track surgical instruments.

RELATED APPLICATION DATA

This application is a continuation of U.S. Ser. No. 10/084,012, filedFeb. 27, 2002 and entitled “Total Knee Arthroplasty Systems andProcesses,” which claims the benefit of U.S. Ser. No. 60/271,818, filedFeb. 27, 2001 and entitled “Image Guided System for Arthroplasty” andU.S. Ser. No. 60/355,899, filed Feb. 11, 2002 and entitled “SurgicalNavigation Systems and Processes,” all of which are incorporated hereinby this reference.

FIELD OF INVENTION

Systems and processes for tracking anatomy, implements, instrumentation,trial implants, implant components and virtual constructs or references,and rendering images and data related to them in connection withorthopedic, surgical and other operations, for example Total KneeArthroplasty (“TKA”). Anatomical structures and such items may beattached to or otherwise associated with fiducial functionality, andconstructs may be registered in position using fiducial functionalitywhose position and orientation can be sensed and tracked by systems andaccording to processes of the present invention in three dimensions inorder to perform TKA. Such structures, items and constructs can berendered onscreen properly positioned and oriented relative to eachother using associated image files, data files, image input, othersensory input, based on the tracking. Such systems and processes, amongother things, allow surgeons to navigate and perform TKA using imagesthat reveal interior portions of the body combined with computergenerated or transmitted images that show surgical implements,instruments, trials, implants, and/or other devices located and orientedproperly relative to the body part. Such systems and processes allow,among other things, more accurate and effective resection of bone,placement and assessment of trial implants and joint performance, andplacement and assessment of performance of actual implants and jointperformance.

BACKGROUND AND SUMMARY

A leading cause of wear and revision in prosthetics such as kneeimplants, hip implants and shoulder implants is less than optimumimplant alignment. In a Total Knee Arthroplasty, for example, currentinstrument design for resection of bone limits the alignment of thefemoral and tibial resections to average values for varus/valgus,flexion/extension, and external/internal rotation. Additionally,surgeons often use visual landmarks or “rules of thumb” for alignmentwhich can be misleading due to anatomical variability. Intramedullaryreferencing instruments also violate the femoral and tibial canal. Thisintrusion increases the risk of fat embolism and unnecessary blood lossin the patient. Surgeons also rely on instrumentation to predict theappropriate implant size for the femur and tibia instead of the abilityto intraoperatively template the appropriate size of the implants foroptimal performance. Another challenge for surgeons is soft tissue orligament balancing after the bone resections have been made. Releasingsome of the soft tissue points can change the balance of the knee;however, the multiple options can be confusing for many surgeons. Inrevision TKA, for example, many of the visual landmarks are no longerpresent, making alignment and restoration of the joint line difficult.The present invention is applicable not only for knee repair,reconstruction or replacement surgery, but also repair, reconstructionor replacement surgery in connection with any other joint of the body aswell as any other surgical or other operation where it is useful totrack position and orientation of body parts, non-body components and/orvirtual references such as rotational axes, and to display and outputdata regarding positioning and orientation of them relative to eachother for use in navigation and performance of the operation.

Several providers have developed and marketed various forms of imagingsystems for use in surgery. Many are based on CT scans and/or MRI dataor on digitized points on the anatomy. Other systems align preoperativeCT scans, MRIs or other images with intraoperative patient positions. Apreoperative planning system allows the surgeon to select referencepoints and to determine the final implant position. Intraoperatively,the system calibrates the patient position to that preoperative plan,such as using a “point cloud” technique, and can use a robot to makefemoral and tibial preparations.

Systems and processes according to one embodiment of the presentinvention use position and/or orientation tracking sensors such asinfrared sensors acting stereoscopically or otherwise to track positionsof body parts, surgery-related items such as implements,instrumentation, trial prosthetics, prosthetic components, and virtualconstructs or references such as rotational axes which have beencalculated and, stored based on designation of bone landmarks.Processing capability such as any desired form of computerfunctionality, whether standalone, networked, or otherwise, takes intoaccount the position and orientation information as to various items inthe position sensing field (which may correspond generally orspecifically to all or portions or more than all of the surgical field)based on sensed position and orientation of their associated fiducialsor based on stored position and/or orientation information. Theprocessing functionality correlates this position and orientationinformation for each object with stored information regarding the items,such as a computerized fluoroscopic imaged file of a femur or tibia, awire frame data file for rendering a representation of aninstrumentation component, trial prosthesis or actual prosthesis, or acomputer generated file relating to a rotational axis or other virtualconstruct or reference. The processing functionality then displaysposition and orientation of these objects on a screen or monitor, orotherwise. Thus, systems and processes according to one embodiment ofthe invention can display and otherwise output useful data relating topredicted or actual position and orientation of body parts, surgicallyrelated items, implants, and virtual constructs for use in navigation,assessment, and otherwise performing surgery or other operations.

As one example, images such as fluoroscopy images showing internalaspects of the femur and tibia can be displayed on the monitor incombination with actual or predicted shape, position and orientation ofsurgical implements, instrumentation components, trial implants, actualprosthetic components, and rotational axes in order to allow the surgeonto properly position and assess performance of various aspects of thejoint being repaired, reconstructed or replaced. The surgeon maynavigate tools, instrumentation, trial prostheses, actual prostheses andother items relative to bones and other body parts in order to performTKA's more accurately, efficiently, and with better alignment andstability. Systems and processes according to the present invention canalso use the position tracking information and, if desired, datarelating to shape and configuration of surgical related items andvirtual constructs or references in order to produce numerical datawhich may be used with or without graphic imaging to perform tasks suchas assessing performance of trial prosthetics statically and throughouta range of motion, appropriately modifying tissue such as ligaments toimprove such performance and similarly assessing performance of actualprosthetic components which have been placed in the patient foralignment and stability. Systems and processes according to the presentinvention can also generate data based on position tracking and, ifdesired, other information to provide cues on screen, aurally or asotherwise desired to assist in the surgery such as suggesting certainbone modification steps or measures which may be taken to releasecertain ligaments or portions of them based on performance of componentsas sensed by systems and processes according to the present invention.

According to a preferred embodiment of systems and processes accordingto the present invention, at least the following steps are involved:

1. Obtain appropriate images such as fluoroscopy images of appropriatebody parts such as femur and tibia, the imager being tracked in positionvia an associated fiducial whose position and orientation is tracked byposition/orientation sensors such as stereoscopic infrared (active orpassive) sensors according to the present invention.

2. Register tools, instrumentation, trial components, prostheticcomponents, and other items to be used in surgery, each of whichcorresponds to a fiducial whose position and orientation can be trackedby the position/orientation sensors.

3. Locating and registering body structure such as designating points onthe femur and tibia using a probe associated with a fiducial in order toprovide the processing functionality information relating to the bodypart such as rotational axes.

4. Navigating and positioning instrumentation such as cuttinginstrumentation in order to modify bone, at least partially using imagesgenerated by the processing functionality corresponding to what is beingtracked and/or has been tracked, and/or is predicted, by the system, andthereby resecting bone effectively, efficiently and accurately.

5. Navigating and positioning trial components such as femoralcomponents and tibial components, some or all of which may be installedusing impactors with a fiducial and, if desired, at the appropriate timediscontinuing tracking the position and orientation of the trialcomponent using the impactor fiducial and starting to track thatposition and orientation using the body part fiducial on which thecomponent is installed.

6. Assessing alignment and stability of the trial components and joint,both statically and dynamically as desired, using images of the bodyparts in combination with images of the trial components whileconducting appropriate rotation, anterior-posterior drawer andflexion/extension tests and automatically storing and calculatingresults to present data or information which allows the surgeon toassess alignment and stability.

7. Releasing tissue such as ligaments if necessary and adjusting trialcomponents as desired for acceptable alignment and stability.

8. Installing implant components whose positions may be tracked at firstvia fiducials associated with impactors for the components and thentracked via fiducials on the body parts in which the components areinstalled.

9. Assessing alignment and stability of the implant components and jointby use of some or all tests mentioned above and/or other tests asdesired, releasing tissue if desired, adjusting if desired, andotherwise verifying acceptable alignment, stability and performance ofthe prosthesis, both statically and dynamically.

This process, or processes including it or some of it may be used in anytotal or partial joint repair, reconstruction or replacement, includingknees, hips, shoulders, elbows, ankles and any other desired joint inthe body.

Such processes are disclosed in U.S. Ser. No. 60/271,818 filed Feb. 27,2001, entitled Image Guided System for Arthroplasty, which isincorporated herein by reference as are all documents incorporated byreference therein.

Systems and processes according to the present invention representsignificant improvement over other, previous systems and processes. Forinstance, systems which use CT and MRI data generally require theplacement of reference frames pre-operatively which can lead toinfection at the pin site. The resulting 3D images must then beregistered, or calibrated, to the patient anatomy intraoperatively.Current registration methods are less accurate than the fluoroscopicsystem. These imaging modalities are also more expensive. Some“imageless” systems, or non-imaging systems, require digitizing a largenumber of points to define the complex anatomical geometries of the kneeat each desired site. This can be very time intensive resulting inlonger operating room time. Other imageless systems determine themechanical axis of the knee by performing an intraoperative kinematicmotion to determine the center of rotation at the hip, knee, and ankle.This requires placement of reference frames at the iliac crest of thepelvis and in or on the ankle. This calculation is also time consumingas the system must find multiple points in different planes in order tofind the center of rotation. This is also problematic in patients with apathologic condition. Ligaments and soft tissues in the arthriticpatient are not normal and thus will give a center of rotation that isnot desirable for normal knees. Robotic systems require expensive CT orMRI scans and also require pre-operative placement of reference frames,usually the day before surgery. These systems are also much slower,almost doubling operating room time and expense.

None of these systems can effectively track femoral and/or tibial trialsduring a range of motion and calculate the relative positions of thearticular surfaces, among other things. Also, none of them currentlymake suggestions on ligament balancing, display ligament balancingtechniques, or, surgical techniques. Additionally, none of these systemscurrently track the patella.

An object of certain aspects of the present invention is to use computerprocessing functionality in combination with imaging and position and/ororientation tracking sensors to present to the surgeon during surgicaloperations visual and data information useful to navigate, track and/orposition implements, instrumentation, trial components, prostheticcomponents and other items and virtual constructs relative to the humanbody in order to improve performance of a repaired, replaced orreconstructed knee joint.

Another object of certain aspects of the present invention is to usecomputer processing functionality in combination with imaging andposition and/or orientation tracking sensors to present to the surgeonduring surgical operations visual and data information useful to assessperformance of a knee and certain items positioned therein, includingcomponents such as trial components and prosthetic components, forstability, alignment and other factors, and to adjust tissue and bodyand non-body structure in order to improve such performance of arepaired, reconstructed or replaced knee joint.

Another object of certain aspects of the present invention is to usecomputer processing functionality in combination with imaging andposition and/or orientation tracking sensors to present to the surgeonduring surgical operations visual and data information useful to showpredicted position and movement of implements, instrumentation, trialcomponents, prosthetic components and other items and virtual constructsrelative to the human body in order to select appropriate components,resect bone accurately, effectively and efficiently, and thereby improveperformance of a repaired, replaced or reconstructed knee joint.

Other objects, features and advantages of the present invention areapparent with respect to the remainder of this document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a particular embodiment of systems andprocesses according to the present invention.

FIG. 2 is a view of a knee prepared for surgery, including a femur and atibia, to which fiducials according to one embodiment of the presentinvention have been attached.

FIG. 3 is a view of a portion of a leg prepared for surgery according tothe present invention with a C-arm for obtaining fluoroscopic imagesassociated with a fiducial according to one embodiment of the presentinvention.

FIG. 4 is a fluoroscopic image of free space rendered on a monitoraccording to one embodiment of the present invention.

FIG. 5 is a fluoroscopic image of femoral head obtained and renderedaccording one embodiment of the present invention.

FIG. 6 is a fluoroscopic image of a knee obtained and rendered accordingto one embodiment of the present invention.

FIG. 7 is a fluoroscopic image of a tibia distal end obtained andrendered according to one embodiment of the present invention.

FIG. 8 is a fluoroscopic image of a lateral view of a knee obtained andrendered according to one embodiment of the present invention.

FIG. 9 is a fluoroscopic image of a lateral view of a knee obtained andrendered according to one embodiment of the present invention.

FIG. 10 is a fluoroscopic image of a lateral view of a tibia distal endobtained and rendered according to one embodiment of the presentinvention.

FIG. 11 shows a probe according to one embodiment of the presentinvention being used to register a surgically related component fortracking according to one embodiment of the present invention.

FIG. 12 shows a probe according to one embodiment of the presentinvention being used to register a cutting block for tracking accordingto one embodiment of the present invention.

FIG. 13 shows a probe according to one embodiment of the presentinvention being used to register a tibial cutting block for trackingaccording to one embodiment of the present invention.

FIG. 14 shows a probe according to one embodiment of the presentinvention being used to register an alignment guide for trackingaccording to one embodiment of the present invention.

FIG. 15 shows a probe according to one embodiment of the presentinvention being used to designate landmarks on bone structure fortracking according one embodiment of the present invention.

FIG. 16 is another view of a probe according to one embodiment of thepresent invention being used to designate landmarks on bone structurefor tracking according one embodiment of the present invention.

FIG. 17 is another view of a probe according to one embodiment of thepresent invention being used to designate landmarks on bone structurefor tracking according one embodiment of the present invention.

FIG. 18 is a screen face produced according to one embodiment of thepresent invention during designation of landmarks to determine a femoralmechanical axis.

FIG. 19 is a view produced according to one embodiment of the presentinvention during designation of landmarks to determine a tibialmechanical axis.

FIG. 20 is a screen face produced according to one embodiment of thepresent invention during designation of landmarks to determine anepicondylar axis.

FIG. 21 is a screen face produced according to one embodiment of thepresent invention during designation of landmarks to determine ananterior-posterior axis.

FIG. 22 is a screen face produced according to one embodiment of thepresent invention during designation of landmarks to determine aposterior condylar axis.

FIG. 23 is a screen face according to one embodiment of the presentinvention which presents graphic indicia which may be employed to helpdetermine reference locations within bone structure.

FIG. 24 is a screen face according to one embodiment of the presentinvention showing mechanical and other axes which have been establishedaccording to one embodiment of the present invention.

FIG. 25 is another screen face according to one embodiment of thepresent invention showing mechanical and other axes which have beenestablished according to one embodiment of the present invention.

FIG. 26 is another screen face according to one embodiment of thepresent invention showing mechanical and other axes which have beenestablished according to one embodiment of the present invention.

FIG. 27 shows navigation and placement of an extramedullary rodaccording to one embodiment of the present invention.

FIG. 28 is another view showing navigation and placement of anextramedullary rod according to one embodiment of the present invention.

FIG. 29 is a screen face produced according to one embodiment of thepresent invention which assists in navigation and/or placement of anextramedullary rod.

FIG. 30 is another view of a screen face produced according to oneembodiment of the present invention which assists in navigation and/orplacement of an extramedullary rod.

FIG. 31 is a view which shows navigation and placement of an alignmentguide according to one embodiment of the present invention.

FIG. 32 is another view which shows navigation and placement of analignment guide according to one embodiment of the present invention.

FIG. 33 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 34 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 35 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 36 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 37 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 38 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 39 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 40 is a screen face which shows a fluoroscopic image of bone incombination with computer generated images of axes and components inaccordance with one embodiment of the present invention.

FIG. 41 is a view showing placement of a cutting block according to oneembodiment of the present invention.

FIG. 42 is a screen face according to one embodiment of the presentinvention which may be used to assist in navigation and placement ofinstrumentation.

FIG. 43 is another screen face according to one embodiment of thepresent invention which may be used to assist in navigation and/orplacement of instrumentation.

FIG. 44 is a view showing placement of an alignment guide according toone embodiment of the present invention.

FIG. 45 is another view showing placement of a cutting block accordingto one embodiment of the present invention.

FIG. 46 is a view showing navigation and placement of the cutting blockof FIG. 45.

FIG. 47 is another view showing navigation and placement of a cuttingblock according to one embodiment of the present invention.

FIG. 48 is a view showing navigation and placement of a tibial cuttingblock according to one embodiment of the present invention.

FIG. 49 is a screen face according to one embodiment of the presentinvention which may be used to assist in navigation and placement ofinstrumentation.

FIG. 50 is another screen face according to one embodiment of thepresent invention which may be used to assist in navigation andplacement of instrumentation.

FIG. 51 is another screen face according to one embodiment of thepresent invention which may be used to assist in navigation andplacement of instrumentation.

FIG. 52 is another screen face according to one embodiment of thepresent invention which may be used to assist in navigation andplacement of instrumentation.

FIG. 53 is another screen face according to one embodiment of thepresent invention which may be used to assist in navigation andplacement of instrumentation.

FIG. 54 is a view showing navigation and placement of a femoralcomponent using an impactor to which a fiducial according to oneembodiment of the present invention is attached.

FIG. 55 is a view showing navigation and placement of a tibial trialcomponent according to one embodiment of the present invention.

FIG. 56 is a view showing articulation of trial components during trialreduction according to one embodiment of the present invention.

FIG. 57 is a screen face according to one embodiment of the presentinvention which may be used to assist in assessing joint function.

FIG. 58 is a screen face according to one embodiment of the presentinvention which may be used to assist in assessing joint function.

FIG. 59 is a screen face according to one embodiment of the presentinvention which may be used to assist in assessing joint function.

FIG. 60 is a screen face according to one embodiment of the presentinvention which contains images and textural suggestions for assistingin assessing performance and making adjustments to improve performanceof a joint in accordance with one aspect of the invention.

FIG. 61 is a screen face according to one embodiment of the presentinvention which contains images and textural suggestions for assistingin assessing performance and making adjustments to improve performanceof a joint in accordance with one aspect of the invention.

FIG. 62 is a screen face according to one embodiment of the presentinvention which contains images and textural suggestions for assistingin assessing performance and making adjustments to improve performanceof a joint in accordance with one aspect of the invention.

FIG. 63 is a screen face according to one embodiment of the presentinvention which contains images and textural suggestions for assistingin assessing performance and making adjustments to improve performanceof a joint in accordance with one aspect of the invention.

FIG. 64 is a computer generated graphic according to one embodiment ofthe present invention which allows visualization of trial or actualcomponents installed in the bone structure according to one embodimentof the invention.

DETAILED DESCRIPTION

Systems and processes according to a preferred embodiment of the presentinvention use computer capacity, including standalone and/or networked,to store data regarding spatial aspects of surgically related items andvirtual constructs or references including body parts, implements,instrumentation, trial components, prosthetic components and rotationalaxes of body parts. Any or all of these may be physically or virtuallyconnected to or incorporate any desired form of mark, structure,component, or other fiducial or reference device or technique whichallows position and/or orientation of the item to which it is attachedto be sensed and tracked, preferably in three dimensions of translationand three degrees of rotation as well as in time if desired. In thepreferred embodiment, such “fidicuals” are reference frames eachcontaining at least three, preferably four, sometimes more, reflectiveelements such as spheres reflective of lightwave or infrared energy, oractive elements such as LEDs.

In a preferred embodiment, orientation of the elements on a particularfiducial varies from one fiducial to the next so that sensors accordingto the present invention may distinguish between various components towhich the fiducials are attached in order to correlate for display andother purposes data files or images of the components. In a preferredembodiment of the present invention, some fiducials use reflectiveelements and some use active elements, both of which may be tracked bypreferably two, sometimes more infrared sensors whose output may beprocessed in concert to geometrically calculate position and orientationof the item to which the fiducial is attached.

Position/orientation tracking sensors and fiducials need not be confinedto the infrared spectrum. Any electromagnetic, electrostatic, light,sound, radiofrequency or other desired technique may be used.Alternatively, each item such as a surgical implement, instrumentationcomponent, trial component, implant component or other device maycontain its own “active” fiducial such as a microchip with appropriatefield sensing or position/orientation sensing functionality andcommunications link such as spread spectrum RF link, in order to reportposition and orientation of the item. Such active fiducials, or hybridactive/passive fiducials such as transponders can be implanted in thebody parts or in any of the surgically related devices mentioned above,or conveniently located at their surface or otherwise as desired.Fiducials may also take the form of conventional structures such as ascrew driven into a bone, or any other three dimensional item attachedto another item, position and orientation of such three dimensional itemable to be tracked in order to track position and orientation of bodyparts and surgically related items. Hybrid fiducials may be partlypassive, partly active such as inductive components or transponderswhich respond with a certain signal or data set when queried by sensorsaccording to the present invention.

Systems and processes according to a preferred embodiment of the presentinvention employ a computer to calculate and store reference axes ofbody components such as in a TKA, for example, the mechanical axis ofthe femur and tibia. From these axes such systems track the position ofthe instrumentation and osteotomy guides so that bone resections willlocate the implant position optimally, usually aligned with themechanical axis. Furthermore, during trial reduction of the knee, thesystems provide feedback on the balancing of the ligaments in a range ofmotion and under varus/valgus, anterior/posterior and rotary stressesand can suggest or at least provide more accurate information than inthe past about which ligaments the surgeon should release in order toobtain correct balancing, alignment and stability. Systems and processesaccording to the present invention can also suggest modifications toimplant size, positioning, and other techniques to achieve optimalkinematics. Systems and processes according to the present invention canalso include databases of information regarding tasks such as ligamentbalancing, in order to provide suggestions to the surgeon based onperformance of test results as automatically calculated by such systemsand processes.

FIG. 1 is a schematic view showing one embodiment of a system accordingto the present invention and one version of a setting according to thepresent invention in which surgery on a knee, in this case a Total KneeArthroplasty, may be performed. Systems and processes according to thepresent invention can track various body parts such as tibia 10 andfemur 12 to which fiducials of the sort described above or any othersort may be implanted, attached, or otherwise associated physically,virtually, or otherwise. In the embodiment shown in FIG. 1, fiducials 14are structural frames some of which contain reflective elements, some ofwhich contain LED active elements, some of which can contain both, fortracking using stereoscopic infrared sensors suitable, at leastoperating in concert, for sensing, storing, processing and/or outputtingdata relating to (“tracking”) position and orientation of fiducials 14and thus components such as 10 and 12 to which they are attached orotherwise associated. Position sensor 16, as mentioned above, may be anysort of sensor functionality for sensing position and orientation offiducials 14 and therefore items with which they are associated,according to whatever desired electrical, magnetic, electromagnetic,sound, physical, radio frequency, or other active or passive technique.In the preferred embodiment, position sensor 16 is a pair of infraredsensors disposed on the order of a meter, sometimes more, sometimesless, apart and whose output can be processed in concert to provideposition and orientation information regarding fiducials 14.

In the embodiment shown in FIG. 1, computing functionality 18 caninclude processing functionality, memory functionality, input/outputfunctionality whether on a standalone or distributed basis, via anydesired standard, architecture, interface and/or network topology. Inthis embodiment, computing functionality 18 is connected to a monitor onwhich graphics and data may be presented to the surgeon during surgery.The screen preferably has a tactile interface so that the surgeon maypoint and click on screen for tactile screen input in addition to orinstead of, if desired, keyboard and mouse conventional interfaces.Additionally, a foot pedal 20 or other convenient interface may becoupled to functionality 18 as can any other wireless or wired interfaceto allow the surgeon, nurse or other desired user to control or directfunctionality 18 in order to, among other things, captureposition/orientation information when certain components are oriented oraligned properly. Items 22 such as trial components, instrumentationcomponents may be tracked in position and orientation relative to bodyparts 10 and 12 using fiducials 14.

Computing functionality 18 can process, store and output on monitor 24and otherwise various forms of data which correspond in whole or part tobody parts 10 and 12 and other components for item 22. For example, inthe embodiment shown in FIG. 1, body parts 10 and 12 are shown incross-section or at least various internal aspects of them such as bonecanals and surface structure are shown using fluoroscopic images. Theseimages are obtained using a C-arm attached to a fiducial 14. The bodyparts, for example, tibia 10 and femur 12, also have fiducials attached.When the fluoroscopy images are obtained using the C-arm with fiducial14, a position/orientation sensor 16 “sees” and tracks the position ofthe fluoroscopy head as well as the positions and orientations of thetibia 10 and femur 12. The computer stores the fluoroscopic images withthis position/orientation information, thus correlating position andorientation of the fluoroscopic image relative to the relevant body partor parts. Thus, when the tibia 10 and corresponding fiducial 14 move,the computer automatically and correspondingly senses the new positionof tibia 10 in space and can correspondingly move implements,instruments, references, trials and/or implants on the monitor 24relative to the image of tibia 10. Similarly, the image of the body partcan be moved, both the body part and such items may be moved, or the onscreen image otherwise presented to suit the preferences of the surgeonor others and carry out the imaging that is desired. Similarly, when anitem 22 such as an extramedullary rod, intramedullary rod, or other typeof rod, that is being tracked moves, its image moves on monitor 24 sothat the monitor shows the item 22 in proper position and orientation onmonitor 24 relative to the femur 12. The rod 22 can thus appear on themonitor 24 in proper or improper alignment with respect to themechanical axis and other features of the femur 12, as if the surgeonwere able to see into the body in order to navigate and position rod 22properly

The computer functionality 18 can also store data relating toconfiguration, size and other properties of items 22 such as implements,instrumentation, trial components, implant components and other itemsused in surgery. When those are introduced into the field ofposition/orientation sensor 16, computer functionality 18 can generateand display overlaid or in combination with the fluoroscopic images ofthe body parts 10 and 12, computer generated images of implements,instrumentation components, trial components, implant components andother items 22 for navigation, positioning, assessment and other uses.

Additionally, computer functionality 18 can track any point in theposition/orientation sensor 16 field such as by using a designator or aprobe 26. The probe also can contain or be attached to a fiducial 14.The surgeon, nurse, or other user touches the tip of probe 26 to a pointsuch as a landmark on bone structure and actuates the foot pedal 20 orotherwise instructs the computer 18 to note the landmark position. Theposition/orientation sensor 16 “sees” the position and orientation offiducial 14 “knows” where the tip of probe 26 is relative to thatfiducial 14 and thus calculates and stores, and can display on monitor24 whenever desired and in whatever form or fashion or color, the pointor other position designated by probe 26 when the foot pedal 20 is hitor other command is given. Thus, probe 26 can be used to designatelandmarks on bone structure in order to allow the computer 18 to storeand track, relative to movement of the bone fiducial 14, virtual orlogical information such as mechanical axis 28, medial lateral axis 30and anterior/posterior axis 32 of femur 12, tibia 10 and other bodyparts in addition to any other virtual or actual construct or reference.

Systems and processes according to an embodiment of the presentinvention such as the subject of FIGS. 2-64, can use the so-calledFluoroNAV system and software provided by Medtronic Sofamor DanekTechnologies. Such systems or aspects of them are disclosed in U.S. Pat.Nos. 5,383,454; 5,871,445; 6,146,390; 6,165,81; 6,235,038 and 6,236,875,and related (under 35 U.S.C. Section 119 and/or 120) patents, which areall incorporated herein by this reference. Any other desired systems canbe used as mentioned above for imaging, storage of data, tracking ofbody parts and items and for other purposes. The FluoroNav systemrequires the use of reference frame type fiducials 14 which have fourand in some cases five elements tracked by infrared sensors forposition/orientation of the fiducials and thus of the body part,implement, instrumentation, trial component, implant component, or otherdevice or structure being tracked. Such systems also use at least oneprobe 26 which the surgeon can use to select, designate, register, orotherwise make known to the system a point or points on the anatomy orother locations by placing the probe as appropriate and signaling orcommanding the computer to note the location of, for instance, the tipof the probe. The FluoroNav system also tracks position and orientationof a C-arm used to obtain fluoroscopic images of body parts to whichfiducials have been attached for capturing and storage of fluoroscopicimages keyed to position/orientation information as tracked by thesensors 16. Thus, the monitor 24 can render fluoroscopic images of bonesin combination with computer generated images of virtual constructs andreferences together with implements, instrumentation components, trialcomponents, implant components and other items used in connection withsurgery for navigation, resection of bone, assessment and otherpurposes.

FIGS. 2-64 are various views associated with Total Knee Arthroplastysurgery processes according to one particular embodiment and version ofthe present invention being carried out with the FluoroNav systemreferred to above. FIG. 2 shows a human knee in the surgical field, aswell as the corresponding femur and tibia, to which fiducials 14 havebeen rigidly attached in accordance with this embodiment of theinvention. Attachment of fiducials 14 preferably is accomplished usingstructure that withstands vibration of surgical saws and otherphenomenon which occur during surgery without allowing any substantialmovement of fiducial 14 relative to body part being tracked by thesystem. FIG. 3 shows fluoroscopy images being obtained of the body partswith fiducials 14 attached. The fiducial 14 on the fluoroscopy head inthis embodiment is a cylindrically shaped cage which contains LEDs or“active” emitters for tracking by the sensors 16. Fiducials 14 attachedto tibia 10 and femur 12 can also be seen. The fiducial 14 attached tothe femur 12 uses LEDs instead of reflective spheres and is thus active,fed power by the wire seen extending into the bottom of the image.

FIGS. 4-10 are fluoroscopic images shown on monitor 24 obtained withposition and/or orientation information received by, noted and storedwithin computer 18. FIG. 4 is an open field with no body part image, butwhich shows the optical indicia which may be used to normalize the imageobtained using a spherical fluoroscopy wave front with the substantiallyflat surface of the monitor 24. FIG. 5 shows an image of the femur 12head. This image is taken in order to allow the surgeon to designate thecenter of rotation of the femoral head for purposes of establishing themechanical axis and other relevant constructs relating to of the femuraccording to which the prosthetic components will ultimately bepositioned. Such center of rotation can be established by articulatingthe femur within the acetabulum or a prosthesis to capture a number ofsamples of position and orientation information and thus in turn toallow the computer to calculate the average center of rotation. Thecenter of rotation can be established by using the probe and designatinga number of points on the femoral head and thus allowing the computer tocalculate the geometrical center or a center which corresponds to thegeometry of points collected. Additionally, graphical representationssuch as controllably sized circles displayed on the monitor can befitted by the surgeon to the shape of the femoral head on planar imagesusing tactile input on screen to designate the centers according to thatgraphic, such as are represented by the computer as intersection of axesof the circles. Other techniques for determining, calculating orestablishing points or constructs in space, whether or not correspondingto bone structure, can be used in accordance with the present invention.

FIG. 5 shows a fluoroscopic image of the femoral head while FIG. 6 showsan anterior/posterior view of the knee which can be used to designatelandmarks and establish axes or constructs such as the mechanical axisor other rotational axes. FIG. 7 shows the distal end of the tibia andFIG. 8 shows a lateral view of the knee. FIG. 9 shows another lateralview of the knee while FIG. 10 shows a lateral view of the distal end ofthe tibia.

Registration of Surgically Related Items

FIGS. 11-14 show designation or registration of items 22 which will beused in surgery. Registration simply means, however it is accomplished,ensuring that the computer knows which body part, item or constructcorresponds to which fiducial or fiducials, and how the position andorientation of the body part, item or construct is related to theposition and orientation of its corresponding fiducial or a fiducialattached to an impactor or other component which is in turn attached toan item. Such registration or designation can be done before or afterregistering bone or body parts as discussed with respect to FIGS. 4-10.FIG. 11 shows a technician designating with probe 26 an item 22 such asan instrument component to which fiducial 14 is attached. The sensor 16“sees” the position and orientation of the fiducial 14 attached to theitem 22 and also the position and orientation of the fiducial 14attached to the probe 26 whose tip is touching a landmark on the item22. The technician designates onscreen or otherwise the identificationof the item and then activates the foot pedal or otherwise instructs thecomputer to correlate the data corresponding to such identification,such as data needed to represent a particular cutting block componentfor a particular knee implant product, with the particularly shapedfiducial 14 attached to the component 22. The computer has then storedidentification, position and orientation information relating to thefiducial for component 22 correlated with the data such as configurationand shape data for the item 22 so that upon registration, when sensor 16tracks the item 22 fiducial 14 in the infrared field, monitor 24 canshow the cutting block component 22 moving and turning, and properlypositioned and oriented relative to the body part which is also beingtracked. FIGS. 12-14 show similar registration for other instrumentationcomponents 22.

Registration of Anatomy and Constructs

Similarly, the mechanical axis and other axes or constructs of bodyparts 10 and 12 can also be “registered” for tracking by the system.Again, the system has employed a fluoroscope to obtain images of thefemoral head, knee and ankle of the sort shown in FIGS. 4-10. The systemcorrelates such images with the position and orientation of the C-armand the patient anatomy in real time as discussed above with the use offiducials 14 placed on the body parts before image acquisition and whichremain in position during the surgical procedure. Using these imagesand/or the probe, the surgeon can select and register in the computer 18the center of the femoral head and ankle in orthogonal views, usuallyanterior/posterior and lateral, on a touch screen. The surgeon uses theprobe to select any desired anatomical landmarks or references at theoperative site of the knee or on the skin or surgical draping over theskin, as on the ankle. These points are registered in three dimensionalspace by the system and are tracked relative to the fiducials on thepatient anatomy which are preferably placed intraoperatively. FIG. 15shows the surgeon using probe 26 to designate or register landmarks onthe condylar portion of femur 12 using probe 26 in order to feed to thecomputer 18 the position of one point needed to determine, store, anddisplay the epicondylar axis. (See FIG. 20 which shows the epicondylaraxis and the anterior-posterior plane and for lateral plane.) Althoughregistering points using actual bone structure such as in FIG. 15 is onepreferred way to establish the axis, a cloud of points approach by whichthe probe 26 is used to designate multiple points on the surface of thebone structure can be employed, as can moving the body part and trackingmovement to establish a center of rotation as discussed above. Once thecenter of rotation for the femoral head and the condylar component havebeen registered, the computer is able to calculate, store, and render,and otherwise use data for, the mechanical axis of the femur 12. FIG. 17once again shows the probe 26 being used to designate points on thecondylar component of the femur 12.

FIG. 18 shows the onscreen images being obtained when the surgeonregisters certain points on the bone surface using the probe 26 in orderto establish the femoral mechanical axis. The tibial mechanical axis isthen established by designating points to determine the centers of theproximal and distal ends of the tibia so that the mechanical axis can becalculated, stored, and subsequently used by the computer 18. FIG. 20shows designated points for determining the epicondylar axis, both inthe anterior/posterior and lateral planes while FIG. 21 shows suchdetermination of the anterior-posterior axis as rendered onscreen. Theposterior condylar axis is also determined by designating points or asotherwise desired, as rendered on the computer generated geometricimages overlain or displayed in combination with the fluoroscopicimages, all of which are keyed to fiducials 14 being tracked by sensors16.

FIG. 23 shows an adjustable circle graphic which can be generated andpresented in combination with orthogonal fluoroscopic images of thefemoral head, and tracked by the computer 18 when the surgeon moves iton screen in order to establish the centers of the femoral head in boththe anterior-posterior and lateral planes.

FIG. 24 is an onscreen image showing the anterior-posterior axis,epicondylar axis and posterior condylar axis from points which have beendesignated as described above. These constructs are generated by thecomputer 18 and presented on monitor 24 in combination with thefluoroscopic images of the femur 12, correctly positioned and orientedrelative thereto as tracked by the system. In the fluoroscopic/computergenerated image combination shown at left bottom of FIG. 24, a“sawbones” knee as shown in certain drawings above which contains radioopaque materials is represented fluoroscopically and tracked usingsensor 16 while the computer generates and displays the mechanical axisof the femur 12 which runs generally horizontally. The epicondylar axisruns generally vertically, and the anterior/posterior axis runsgenerally diagonally. The image at bottom right shows similarinformation in a lateral view. Here, the anterior-posterior axis runsgenerally horizontally while the epicondylar axis runs generallydiagonally, and the mechanical axis generally vertically.

FIG. 24, as is the case with a number of screen presentations generatedand presented by the system of FIGS. 4-64, also shows at center a listof landmarks to be registered in order to generate relevant axes andconstructs useful in navigation, positioning and assessment duringsurgery. Textural cues may also be presented which suggest to thesurgeon next steps in the process of registering landmarks andestablishing relevant axes. Such instructions may be generated as thecomputer 18 tracks, from one step to the next, registration of items 22and bone locations as well as other measures being taken by the surgeonduring the surgical operation.

FIG. 25 shows mechanical, lateral, anterior-posterior axes for the tibiaaccording to points are registered by the surgeon.

FIG. 26 is another onscreen image showing the axes for the femur 12.

Modifying Bone

After the mechanical axis and other rotation axes and constructsrelating to the femur and tibia are established, instrumentation can beproperly oriented to resect or modify bone in order to fit trialcomponents and implant components properly according to the embodimentof the invention shown in FIGS. 4-64. Instrumentation such as, forinstance, cutting blocks, to which fiducials 14 are mounted, can beemployed. The system can then track instrumentation as the surgeonmanipulates it for optimum positioning. In other words, the surgeon can“navigate” the instrumentation for optimum positioning using the systemand the monitor. In this manner, instrumentation may be positionedaccording to the system of this embodiment in order to align theostetomies to the mechanical and rotational axes or reference axes on anextramedullary rod that does not violate the canal, on an intramedullaryrod, or on any other type of rod. The touchscreen 24 can then alsodisplay the instrument such as the cutting block and/or the implantrelative to the instrument and the rod during this process, in order,among other things, properly to select size of implant and perhapsimplant type. As the instrument moves, the varus/valgus,flexion/extension and internal/external rotation of the relativecomponent position can be calculated and shown with respect to thereferenced axes; in the preferred embodiment, this can be done at a rateof six cycles per second or faster. The instrument position is thenfixed in the computer and physically and the bone resections are made.

FIG. 27 shows orientation of an extramedullary rod to which a fiducial14 is attached via impactor 22. The surgeon views the screen 24 whichhas an image as shown in FIG. 29 of the rod overlain on or incombination with the femur 12 fluoroscopic image as the two are actuallypositioned and oriented relative to one another in space. The surgeonthen navigates the rod into place preferably along the mechanical axisof the femur and drives it home with appropriate mallet or other device.The present invention thus avoids the need to bore a hole in themetaphysis of the femur and place a reamer or other rod into themedullary canal which can cause fat embolism, hemorrhaging, infectionand other untoward and undesired effects.

FIG. 28 also shows the extramedullary rod being located. FIG. 29 showsfluoroscopic images, both anterior-posterior and lateral, with axes, andwith a computer generated and tracked image of the rod superposed or incombination with the fluoroscopic images of the femur and tibia. FIG. 30shows the rod superposed on the femoral fluoroscopic image similar towhat is shown in FIG. 29.

FIG. 29 also shows other information relevant to the surgeon such as thename of the component being overlain on the femur image (new EM nail),suggestions or instructions at the lower left, and angle of the rod invarus/valgus and extension relative to the axes. Any or all of thisinformation can be used to navigate and position the rod relative to thefemur. At a point in time during or after placement of the rod, itstracking may be “handed off” from the impactor fiducial 14 to the femurfiducal 14 as discussed below.

Once the extramedullary rod, intramedullary rod, other type of rod hasbeen placed, instrumentation can be positioned as tracked in positionand orientation by sensor 16 and displayed on screen face 24. Thus, acutting block of the sort used to establish the condylar anterior cut,with its fiducial 14 attached, is introduced into the field andpositioned on the rod. Because the cutting block corresponds to aparticular implant product and can be adjusted and designated on screento correspond to a particular implant size of that product, the computer18 can generate and display a graphic of the cutting block and thefemoral component overlain on the fluoroscopic image as shown in FIGS.33-36. The surgeon can thus navigate and position the cutting block onscreen using not only images of the cutting block on the bone, but alsoimages of the corresponding femoral component which will be ultimatelyinstalled. The surgeon can thus adjust the positioning of the physicalcutting block component, and secure it to the rod in order to resect theanterior of the condylar portion of the femur in order to optimally fitand position the ultimate femoral component being shown on the screen.FIG. 32 is another view of the cutting block of FIG. 31 beingpositioned. Other cutting blocks and other resections may be positionedand made similarly on the condylar component.

In a similar fashion, instrumentation may be navigated and positioned onthe proximal portion of the tibia 10 as shown in FIG. 41 and as trackedby sensor 16 and on screen by images of the cutting block and theimplant component as shown in FIGS. 37-40. FIGS. 42 and 43 show otheronscreen images generated during this bone modification process forpurposes of navigation and positioning cutting blocks and otherinstrumentation for proper resection and other modification of femur andtibia in order to prepare for trial components and implant componentsaccording to systems and processes of the embodiment of the presentinvention shown in FIGS. 4-64.

FIGS. 44-48 also show instrumentation being positioned relative to femur12 as tracked by the system for resection of the condylar component inorder to receive a particular size of implant component. Various cuttingblocks and their attached fiducials can be seen in these views.

FIG. 49 shows a femoral component overlaid on the femur asinstrumentation is being tracked and positioned in order for resectionof bone properly and accurately to be accomplished. FIG. 50 is anothernavigational screen face showing a femoral component overlay asinstrumentation is being positioned for resection of bone.

FIG. 51 is tibial component overlay information on a navigation screenas the cutting block for the tibial plateau is being positioned for boneresection.

FIGS. 52 and 53 show femoral component and tibial component overlays,respectively, according to certain position and orientation of cuttingblocks/instrumentation as bone resections are made. The surgeon can thusvisualize where the implant components will be and can assess fit, andother things if desired, before resections are made.

Navigation, Placement and Assessment of Trials and Implants

Once resection and modification of bone has been accomplished, implanttrials can then be installed and tracked by the system in a mannersimilar to navigating and positioning the instrumentation, as displayedon the screen 24. Thus, a femoral component trial, a tibial plateautrial, and a bearing plate trial may be placed as navigated on screenusing computer generated overlays corresponding to the trials.

During the trial installation process, and also during the implantcomponent installation process, instrument positioning process or at anyother desired point in surgical or other operations according to thepresent invention, the system can transition or segue from tracking acomponent according to a first fiducial to tracking the componentaccording to a second fiducial. Thus, as shown as FIG. 33, the trialfemoral component is mounted on an impactor to which is attached afiducial 14. The trial component is installed and positioned using theimpactor. The computer 18 “knows” the position and orientation of thetrial relative to the fiducial on the impactor (such as by priorregistration of the component attached to the impactor) so that it cangenerate and display the image of the femoral component trial on screen24 overlaid on the fluoroscopic image of the condylar component. At anydesired point in time, before, during or after the trial component isproperly placed on the condylar component of the femur to align withmechanical axis and according to proper orientation relative to otheraxes, the system can be instructed, by foot pedal or otherwise to begintracking the position of the trial component using the fiducial attachedto the femur rather than the one attached to the impactor. According tothe preferred embodiment, the sensor 16 “sees” at this point in timeboth the fiducials on the impactor and the femur 12 so that it already“knows” the position and orientation of the trial component relative tothe fiducial on the impactor and is thus able to calculate and store forlater use the position and orientation of the trial component relativeto the femur 12 fiducial. Once this “handoff” happens; the impactor canbe removed and the trial component tracked with the femur fiducial 14 aspart of or moving in concert with the femur 12. Similar handoffprocedures may be used in any other instance as desired in accordancewith the present invention.

FIG. 55 shows the tibial plateau trial being tracked and installed in amanner similar to femoral component trial as discussed above.Alternatively, the tibial trial can be placed on the proximal tibia andthen registered using the probe 26. Probe 26 is used to designatepreferably at least three features on the tibial trial of knowncoordinates, such as bone spike holes. As the probe is placed onto eachfeature, the system is prompted to save that coordinate position so thatthe system can match the tibial trial's feature's coordinates to thesaved coordinates. The system then tracks the tibial trial relative tothe tibial anatomical reference frame.

Once the trial components are installed, the surgeon can assessalignment and stability of the components and the joint. During suchassessment, in trial reduction, the computer can display on monitor 24the relative motion between the trial components to allow the surgeon tomake soft tissue releases and changes in order to improve the kinematicsof the knee. The system can also apply rules and/or intelligence to makesuggestions based on the information such as what soft tissue releasesto make if the surgeon desires. The system can also display how the softtissue releases are to be made.

FIG. 56 shows the surgeon articulating the knee as he monitors thescreen which is presenting images such as those shown in FIGS. 57-59which not only show movement of the trial components relative to eachother, but also orientation, flexion, and varus/valgus data. During thisassessment, the surgeon may conduct certain assessment processes such asexternal/internal rotation or rotational laxity testing, varus/valgustests, and anterior-posterior drawer at 0 and 90 degrees and mid range.Thus, in the AP drawer test, the surgeon can position the tibia at thefirst location and press the foot pedal. He then positions the tibia atthe second location and once again presses the foot pedal so that thecomputer has registered and stored two locations in order to calculateand display the drawer and whether it is acceptable for the patient andthe product involved. If not, the computer can apply rules in order togenerate and display suggestions for releasing ligaments or othertissue, or using other component sizes or types, such as shown, forexample, in FIGS. 60-63. Once the proper tissue releases have been made,if necessary, and alignment and stability are acceptable as notedquantitatively on screen about all axes, the trial components may beremoved and actual components navigated, installed, and assessed inperformance in a manner similar to that in which the trial componentswere navigated, installed, and assessed.

FIG. 64 is another computer generated 3-dimensional image of the trialcomponents as tracked by the system during trialing.

At the end of the case, all alignment information can be saved for thepatient file. This is of great assistance to the surgeon due to the factthat the outcome of implant positioning can be seen before anyresections have been made to the bone. The system is also capable oftracking the patella and resulting placement of cutting guides and thepatellar trial position. The system then tracks alignment of the patellawith the patellar femoral groove and will give feedback on issues, suchas, patellar tilt.

The tracking and image information provided by systems and processesaccording to the present invention facilitate telemedical techniques,because they provide useful images for distribution to distantgeographic locations where expert surgical or medical specialists maycollaborate during surgery. Thus, systems and processes according to thepresent invention can be used in connection with computing functionality18 which is networked or otherwise in communication with computingfunctionality in other locations, whether by PSTN, information exchangeinfrastructures such as packet switched networks including the Internet,or as otherwise desire. Such remote imaging may occur on computers,wireless devices, videoconferencing devices or in any other mode or onany other platform which is now or may in the future be capable ofrending images or parts of them produced in accordance with the presentinvention. Parallel communication links such as switched or unswitchedtelephone call connections may also accompany or form part of suchtelemedical techniques. Distant databases such as online catalogs ofimplant suppliers or prosthetics buyers or distributors may form part ofor be networked with functionality 18 to give the surgeon in real timeaccess to additional options for implants which could be procured andused during the surgical operation.

1-20. (canceled)
 21. A computer system for facilitating a jointarthroplasty procedure on a patient's joint, the patient's jointincluding at least one bone, the computer system comprising: (a) aninput that receives image data about a structure of the at least onebone; (b) a memory that at least temporarily stores: (i) the image dataabout the structure of the at least one bone; (ii) reference data aboutat least one reference related to the structure of the at least onebone; and (iii) device data about a surgical device; (c) a processorthat accesses the image, reference and device data at least temporarilystored in the memory and identifies a desired position and orientationof the surgical device relative to the at least one bone of thepatient's joint based at least in part on the image, reference anddevice data; and (d) an output that outputs information about thedesired position and orientation of the surgical device relative to theat least one bone.
 22. The computer system of claim 21, wherein theprocessor identifies the desired position and orientation of thesurgical device relative to the at least one bone of the patient's jointbased at least in part on the image, reference and device data as wellas a surgeon's input.
 23. The computer system of claim 21, wherein thedesired position and orientation of the surgical device determines anactual position and orientation of the surgical device.
 24. The computersystem of claim 21, wherein the desired position and orientation of thesurgical device determines an actual position and orientation of asecond surgical device.
 25. The computer system of claim 21, furthercomprising a display that displays a representation of the structure ofthe at least one bone.
 26. The computer system of claim 25, wherein thedisplay displays a representation of the at least one reference relativeto the representation of the structure of the at least one bone.
 27. Thecomputer system of claim 25, wherein the display displays arepresentation of the desired position and orientation of the surgicaldevice relative to the at least one bone.
 28. The computer system ofclaim 25, wherein the display displays a representation of an actualposition and orientation of the surgical device relative to the at leastone bone.
 29. The computer system of claim 27, wherein the surgicaldevice is a surgical cutting guide.
 30. The computer system of claim 27,wherein the surgical device is an orthopaedic implant.
 31. The computersystem of claim 21, wherein the input also receives the reference data.32. The computer system of claim 31, wherein the reference data is atleast one reference point on the structure of the at least one bone. 33.The computer system of claim 32, wherein the at least one referencepoint is at least one point on a femoral condyle or a trochlear groove.34. The computer system of claim 31, wherein the reference data is acenter of rotation of the at least one bone.
 35. The computer system ofclaim 31, wherein the processor determines an axis of the at least onebone using the reference data.
 36. The computer system of claim 35,wherein the axis is a mechanical axis, an anterior/posterior axis, or amedial/lateral axis of the at least one bone.
 37. The computer system ofclaim 21, wherein the desired position and orientation of the surgicaldevice relative to the at least one bone includes at least one of adesired varus/valgus orientation of the surgical device relative to theat least one bone, a desired internal/external rotation of the surgicaldevice relative to the at least one bone, and a desiredflexion/extension of the surgical device relative to the at least onebone.
 38. The computer system of claim 21, wherein the image data isX-ray image data, CT image data, MRI image data, or fluoroscopic imagedata.
 39. The computer system of claim 21, further comprising a positionsensor for tracking the position of the at least one bone and thesurgical device.
 40. The computer system of claim 21, wherein the outputoutputs information about the desired position and orientation of thesurgical device relative to the structure of the at least one bone. 41.The computer system of claim 21, wherein the computer system is anetworked computer system.
 42. The computer system of claim 21, whereinthe device data is data about a surgical cutting block.
 43. The computersystem of claim 42, wherein the data about the surgical cutting block iswire frame data.
 44. The computer system of claim 21, wherein the jointarthroplasty procedure is a total joint arthroplasty procedure or apartial joint arthroplasty procedure.
 45. The computer system of claim21, wherein the joint arthroplasty procedure is a knee arthroplasty, ahip arthroplasty, a shoulder arthroplasty, an elbow arthroplasty or anankle arthroplasty.
 46. The computer system of claim 21, wherein thejoint arthroplasty procedure is a knee arthroplasty procedure, whereinthe at least one bone is a femur of the patient and a tibia of thepatient, and wherein the image data is about the patient's femur andtibia, including at least portions of an upper and a lower extremity ofthe femur and an upper and lower extremity of the tibia.
 47. Thecomputer system of claim 21, wherein the surgical device is a kneearthroplasty cutting guide that includes an interior surface forcontacting the at least one bone.
 48. The computer system of claim 47,wherein at least a portion of the interior surface of the kneearthroplasty cutting guide is concave.
 49. A computer system forfacilitating a joint arthroplasty procedure on a patient's joint, thepatient's joint including at least one bone, the computer systemcomprising: (a) an input that receives image data about a structure ofthe at least one bone; (b) a memory that at least temporarily stores:(i) the image data about the structure of the at least one bone; (ii)reference data about at least one reference related to the structure ofthe at least one bone; and (iii) device data about a surgical device;(c) a processor that: (1) accesses the image, reference and device dataat least temporarily stored in the memory and identifies a desiredposition and orientation of the surgical device relative to the at leastone bone of the patient's joint based at least in part on the image,reference and device data, and (2) determines a mechanical axis or ananatomic axis of the at least one bone using the reference data; and (d)an output that outputs information about the desired position andorientation of the surgical device relative to the at least one bone.50. The computer system of claim 49, wherein the processor identifiesthe desired position and orientation of the surgical device relative tothe at least one bone of the patient's joint based at least in part onthe image, reference and device data as well as a surgeon's input. 51.The computer system of claim 49, wherein the desired position andorientation of the surgical device determines an actual position andorientation of the surgical device.
 52. The computer system of claim 49,wherein the desired position and orientation of the surgical devicedetermines an actual position and orientation of a second surgicaldevice.
 53. The computer system of claim 49, further comprising adisplay that displays a representation of the structure of the at leastone bone.
 54. The computer system of claim 49, wherein the anatomic axisis an anterior/posterior axis or a medial/lateral axis of the at leastone bone.